Cab signaling amd train control system for  railways



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CAB SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILWAYS Original Filed Feb'. 24. 1920 i3 Sheets-Sheet 3 March 6, 1928. 1,661,670

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GAB SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILWAYS Original Filed Feb. 24, 1920 13 Sheets-Sheet 5 March 6, 192s. 1,661,670

J. A. MILLER ET AL CAB SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILWAYS original Filed Feb. 24, 1920 15 sheets-Sheet 6 y forngs March 6, 1928.

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March 6, 1928.

J. A. MILLER ET AL GABl SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILWAYS 13 Sheets-Shqet 9 Original Filed Feb. 24, 1920 Mmh 6, 192s. 1,661,670

\ J. A. MILLER ET AL CAB" SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILwAYs Original Filed Feb. 24. 1920 15 Sheets-Sheet 10 mam, 7m

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J. A. MILLER ET AL CAB SIGNALING AND TRAIN CONTROL SYSTEM FOR RAILWAYS Ornal Filed Feb. 24. 1920 13 Sheets-Shout 11 www3.

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Patented Mar. 6, 1928.

UNITED STATES PATENT FFICF.

JOHN A. MILLER AND GILBERT W. CATTELL, OF WAUKEGAN, ILLINOIS, ASSIGNORS, EY MESNE ASSIGNMENTS, T() UNION SWITH SGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

CAB-SIGNALING AND TRAIN-CONTROL, SYSTEM FOR RAILVAYS.

Application led February 24, 1920,. Serial This invention relates to cab signaling and train control systems for railways employing electro-magnetic waves for controlling movable units as well as the giving of signals thereon.

The objects and advantages will appear and be set out as the description of the in-. vention progresses, in connection with the accompanying drawings which form a part hereoit, and the new and novel features of the invention will. be particularly pointed out in the appended claims.

In the drawings,

liigure l is a diagram of a double track system embodying the novel features of my invention.

Figure 2 is a diagrammatic view of a single track system embodying the novel fea.- tures ot my invention.

Figure 3 is a diagram illustrating a modiiied arrangement of the wave wires.

liigure 4: is a diagrammatic view illustrating the method of mounting the antennae upon movable unit.

Figure 5 is a diagram of the train system carried by the locomotive or other movable unit.

Figure 6 diagrammatically illustrates a modiiled torni ot' the train system carried by the locomotive or other movable unit, provision being made in the system for an automatic application of brakes in a block ai'ljoining an occupied block, and a second application of brakes at the entrance of the occupied block Figure 7 is a diagram of a further moditication oit the train system carried by the locomotive or other movable unit, the system having device responsive to the beat requency ot the oscillations propagated by the wave wires.

Figure 8 iliagrammatically illustrates the circuits and apparatus associated with one track ot a double track system, the system having means controlled by conditions of safety, caution or danger for propagating radio frequent oscillations, the means comprising main and auxiliary wave wires.

Figure 9 is a diagram illustrating a train system adapted to be carried by a movable No. 360,751. Renewed December 21, 3,927.

unit, the train system comprising means adapted to cooperate with the track systems illustrated in Figures 8 and l0.`

Figure l0 diagrammatically illustrates the circuits and apparatus associated with one track oi. a double track system, the system having' wave wires for propagating radio frequent oscillations, and means dependent upon conditions ot safety, caution or danger for controlling the propagation of the radio frequent oscillations.

Figure ll diagrammatically illustrates the circuits and apparatus associated with one track of a double track system, the system having by-passes between contiguous wave wires, and a balancing circuit for each wave wire.

Figure 12 is a diagram of a train circuit having means adapted to co-operate with the track system illustrated in Figure 11.

4 Figure 13 diagrammatically illustrates a track system for a single track railway, circuits in the track system being similar to those of the track system shown` in Figure ll.

Figure 14 diagrammatically illustrates a modified form of my invention comprising a track system wherein means are provided for giving a visual indication of any change in the conditions oi safety, caution or danger existing in a co-operating track system.

In the drawings like reference characters designate like parts in the several views.

Referring to Figure l, we have there illusy trated part of a double track system in j which 1 and l are the running rails, which are divided into blocks by insulated rail joints 2. The blocks of the west bound track are designated A, B, C and D, and the blocks of the east bound track are designated as A', B, C', and D. The several blocks are preferably of the same length and are so' positioned longitudinally of the tracks that the insulated rail joints 2 ot' one track are directly opposite the insulated rail joints 2 of the other track. Thus each block of each track is paired with al block of the other track. EachA block is provided with a wave wire common to both tracks in the block, the wave wires being designated alternately by ill the reference characters 3 and 4. Thus the wave wires 3 are associated With the blocks A and B and, C and B', while the wave wires are associated with the blocks B and C. and l) and A.

In Figure 1, 5 is an alternating current power feed circuit of suitable voltage, paral- 'le'ling the railway, from which power is suppliedt-hrough leads 0 and 7 to track transformers, 9, which furnish current at 8 to l2 volts for the track circuits ofy the various blocks in accordance with usual practice. and 11 are the. leads from the rails of the eastbound track circuits to the relays 12 assigned tol the several blocks. Relays 12 are Plovideil ii'ith armatures 13;v 14 and 16 are the leads from the power circuit 5 to rectitiers, which may be in the form of motorgenerator sets 15-17. 18 and 19 are direct current leads from the rectifier. are con densers. 21 are leads from the contacts ot' the several armatures 13 to the plate coil windings 27 of hieh frequency generators 22,l and to the plate coil windings 33 of high` frequency generators (only one being shown). 18 and 24 are direct current leads to the several frequency generators. The high frequency generators 22 and 30 are shown` and described as vacuum valves of the pliotion type, but we do not wish to limit ourn selves to the use of high frequency generators of this type and therefore the generators hat Te been di agraiiiiinatically illustrated as `we do not claim the specific details. The structure and operation of high frequency .generators comprising vacuum valves are well known to those skilled in the art and a general description of them is sufficient for the purposes of this application. The plate coil windings 27 and 33 of the generators 22 and 30 are .associated with coil windings. 26 and 32 r ,siieetively 'l1 he windings 2.0 and 27 are inductiiiely wound relatively to and serve as primary windings for a secondary winding 28. The `wirulings and are similarly associated with secondary windings 34. Each seconda-ry winding 28 is connected to a wave wire 3 hy a lead 20 and cach second.- ary winding 34, is connected to a wave wire 4 by a lead 35. track rails of the west bound tracks to the track relays 38. Each relay 38 is provided with. an armature 39. Each armature 39 when attracted by its respective relay is adapted to engage a contact to which one end of a lead 40 is connected. rvthe purpose of this structure will presently appear.

ln addition to the high frequency genera-l tors 22 and 30, we provide a plurality of liighA frequency generators 4l and 47 similar in construction and operationA to the aforemen-` tioned generators 22 .and 30. f The generators 41 and 47 have secondary windings 45 and 51 respectively and plate coil windings 44: and respectively. The generators 41 and 36 and 37 leads from the.

set up in the secondary 28.

47 also have grid coil windings 43 and 49 respectively which function as do the aforementioned windings 26 and 82. Each of the plate coil windings 44 and 50 has o-ne terminal connected to one of the leads 40. Each secondary winding 45 is connected to a wave wire 4 by a lead 46 and each secondary winding 51 is connected to a wave wire 3 by a lead 52.

Each of the generators 22, 30, 41 and 47 is suitably adjusted in a well known manner to impressa high frequency current of delinite frequency upon the wave wire to which it is assigned. For convenience we have designated uponthe drawing the frequencies to which these generators might very well be adjustedin. a commercial system. Thus it willhe noted that generators 22 are adjusted to impress currents of a frequency of 22,000 upon wave wires 3, that generator 47 iinpresses a current of 37,500 frequency upon its associated wave wire 3, that generator 30 impresses a current of 27 ,000 frequency upon its associated wave wire 4, and that genera.- tors 41 impress currentsof 30,000 frequency upon their associated wave wires 4.

Normally all of the high frequency generators 22, 47 30 and 41 are operating and energizing their corresponding wave wires so that the latter are constantly radiating electro-magnetic waves; this because the track relays associated with the several generators are normally energized maintaining the generator circuits closed. Y

Now let us see how the generators assigned to the several blocks of the east bound track are controlled.

Bloc/a B.

The track circuit of block A is supplied with alternating current` of Sl to l2 volts from track transformer 9 (not shown). The. current flows along the rail l of the block A" the current being impressed upon the rail by .its associated track lrans'toriner S). From the designatedv rail 1 the current is conducted to the associated relay 12 hy the lead 11. The current then flows through the winding ot' the relay 12 through the lead V10 and hack along the rail 1 of bloei: Av to the designated track transformer 9. This current energizes the relay 12 and its armature 13 is attracted. yThe attraction of the armature 13 closes a circuit whereby direct current flows from theV rectifier 17 through leads 1.8 and 24 to the grid of a generator 22. The plate being vconnected at this time to the other pole of the rectifier 17, an impingement of electrons takes place upon the plate 25, and hence oscillations are Generator 22 being adjusted to produce a current of 22,000 frequency, this current of 22,000 frequency is transmitted fromV the secondary winding 28 of the transformer of generator y ondary Winding.

electro-magnetic waves radiating therefrom throughout its entire length indicate to east bound traffic in block D that block E is clear.

The severalequipments assigned to blocks C, B, A, etc., alternately function for east bound traffic in all respects as do the equipments assigned to blocks E and D respectively.

The equipment assigned to block C, which includes high frequency generator 47 normally functions for West bound traffic as folloi's:

The relay l2 of the block B yis energized by a current flowing from one terminal of the secondary winding` of the track transformer 9 associated with block B, the current flowingthrough the lead Si', rail l, lead ll, relay l2, lead l0, rail l and through the lead 36 to the other terminal. of the sec- .ihe relay l2 attracts its armatures 13 and `30. rThe armature 39 closes a circuit which permits current to flow from one of the direct current feeders 5 through lead 24, armature 39, lead 40, generator 47 and through the lead 23 to the other of the direct current feeders 5. Current of a frequency of 37,500 will therefore be transmitted to lead 52 and thence to Wave wire 3 of block C and the electro-magnetic Waves radiating` therefrom throughout its entire length indicate to West bound traffic in block C that block B is clear.

The equipment assigned to block D normally functions for West bound traffic in the saine manner as does the equipment assigned to block C, high frequency generator 4l being adjusted to produce current of 30,000 frequency which is transmitted through lead 46 to Wave Wire 4 of block D, the electromagnetic Waves radiatingr therefrom throughout its entire length indicating to west bound traffic in block D that block C is clear.

lhe several equipments assignedto blocks E, F, if, etc., alternately function for West bound traffic in all respects as do the equipments assigned to blocks C and D respectively.

Figure 3 illustrates a modified arrangement of the Wave Wires B and 4. T his view shoivs the Wave Wires 3 and 4 disposed end to end, being separated by a few inches instead of overlapping', as in Figures l and 2.

ln the arrangements shoivn in Figures 'l and 2 the Wave wires are normally7 alternately radiating frequenciesI of 22.000 and 27,000 for east bound traffic and for West bound traffic they alternately radiate frequences of 30,000 and 37,500.

In Figures l and 2 theI Wave Wires 3 and 4 are shoivn overlapping, and in Figure 3- they are shown as in abutting, or end toend, relation, to provide in either instance for the pick-up feature heretofore mentioned. `We now set forth this generic feature of the invention. At the ends of the overlapping or abutting Wave wires 3 vand 4 there Willbe radiated, in the immediate Zone thereof, waves of predetermined frequencies for the direction ofv trafficfor which they are energized. Suitable responsive devices carried by a car or engine and adjusted to respond to the predetermined frequencies at 'the block ends for the direction of traffic which iiie waves are radiated to control, will close their responsii'e relays simultaneously, thereby providing the pick-up feature as accomplislied by the auxiliary wave ivirev as shown and set out in the copendiug application of lohn M'ller Serial No. 275,339, filed February l, i010. present invention is secured by adjusting the detecting devices to respond to a resultant beat frequency inthe .immediate Zone of the abutting' or over-lapping of the ivave Wires.

Ficure 4 illustrates a movable unit, a locomotive, equipped with antennae suitable for j'iiclrin;` u p practically a constant amount of energy from he radiating waveivires 3 and 4 t of Figures l., 2 and 3) throughout their entire length. This is accomplished by the combination of a flat top antenna 53- With loop antenna 54, which are carried upon the sine of the boiler, and upon the side of the cab respectively. A second flattop antenna 53 and a second loop antenna 54 are vplaced on the opposite side of the boiler and top of cab respect'vely. G0 is the apparatus case placed' for convenience upon the running board in front of the cab of the movable unit. 55 is the lead from antenna 53 to apparatus case 60, Where it is joined by lead 57 from loop antenna 54. 56 is the common lead from antennae 53 and 54, connected by lead 58 to responsive device 60. 57 and 57 are the leads from loop antennae 54 and 54 to the responsive device 60, thence to ground.

The combination antennae disclosed in Figure 4 is found very desirable in practice in that it affords a means of obtaining a uniform amount of energy radiated from the wave Wires throughout their entire length. As it is known tol those familiar with this art, when a circuit comprising a simple horizontal antenna, with its distributed inductance and capacityis oscillating;i at its natural period, the current and electromotiife force Will distribute themselves along the conductor according' to the lau' of sine and cosine. That is, the current will be a maximum at the source, diminishing to a minimum at the free end. On the other hand, the electromotive force .is a minimum at the source. increasing to a maximum at the free end. The total energy present at any point along the conductor is constant, ,being entirely electro-magnetic at the source and entirely electro-static at the free end andinade up in part of each betvveen'these tivo points. lf oscillatory currents of different fre- A modified feature of the Y llO quencies are to be received on a movable unit, and tivo sets of antennae provided therefor, as is shown in Figure 4, it is desirable to have the antennae loops separated as tar as practicable or to have an etlective means whereby to eliminate the interference between the tiro. (lne Way to accomplish this is to place tliein at right angles as indicated.

litigare shows diagrainniatically the rensive devices olf a movable unit, in which t1 is the antenna and 02, 0?) and 64 are leads troni the antenna 01 to transformers 05 and i2-l respectively of detectors 0T and T5. 00 and Tft are the adjustablr-e condensers of delector@l 0i" and T5. Leads 055 and 69 connect detector 07 with relay 70. ll and .79 are the armatures olf relay 70. Leads 'l0 and T7 connect detector l5 to relay 78. i 9 and 80 are armatures of relay 78. 82 and 93 are the front contacts of armatures 71 and 79. Connected between contacts 92 and 83 .is

end of bloclr indicator 81, provided with its local battery 89. 8l and 85 are the front ontactirof armatures l2 and 80 respectively. o and dT are the baci; contacts of urinatures (2 and 80 respectively. lis the lead 'troni pivots of arn'iatures T1 and 72 to battery 90. 91 and 92 are leads frein armatures 79 and 50` respectively to a sloiv acting relay Sill and armature 95. 923 is lead and front cmitact to ari'nature 95. 95 and 96 are the arniatures of relay 9-1. 97 and 98 are the front and haelt contactsiof arinature 9G. 99 is a le d 'roin relay 9i to battery conductor lili. is a lead frein battery conductor 115 to relay 101. 102 an li103 are armatures of relay 101. 104,- is a lead troni the front ro ict of inature 102. isa lead frein 01 to junction of leans 104.- and 10G. 10i la a normally open push button. 108 is lead from p'f'l button 10T to lead 90. 109 ront contact and lead troni armature "l is the baclr contact and lead from 5, 103 to whistle valve solenoid 111. lead from armature l?) to train lvl` solenoid 113. 11st 1s lead freni ntact to ,green signal lainp Cr.. s lead frein green signal lanip G to 11G is al lead froin red signal i 117 connnon load frein 'Whistle and train line valve solenoids 111 and 113, respectively, to battery 90. rlllie responsive devices of Figure 5 When rrrried on a ino'rable unit such as a-car or locomotive function as follows: Assume that dote :tors 6i' and T5 are adjusted to respond to waves of 99,000 frequency` and 2?',000 frequency respectively, and that the inovable unit is t aveling,l east through the blocks of if* jure l The relays 70 and 70 will be closed '-.vhoncrer the movable unit .is in the :te zone of the bloclr ends for here the antenna 0l will piel; up both frequencies frein the two acont nave vires, and conly arinatui f "il and will close :nella en i against their front contacts S2 and 84 and armatures 79 and 80 will be closed against their front contacts 83 anc and While the movable unit is in this position block ends, the bloclr end indicating device il, a signal lainp, willbe liv'hted but will cease to gire bloclr end indication when the movable unit passes out of the blcclr end Zone, it being` understood that the bloclr end signal indicater will only function when the antenna is simultaneously receiving Waves of both fre quencies.

l/Vith inovable unit equipment ot Figure 5 at a block end zone, the apparatus functions as follows: Current from battery 90 tlows through the closed circuit comprising lead 8S, armature 71, Contact and leadf, end of block indicator l, lead and contact 83, armature i9, lead 91, relay 94:, leads 99 and 115, back to battery 90. `Relay 94: is thus energized and holds its armatures 95 and, 90 against front contacts 93 and 97, respectively. against their said front contacts serves to close local circuits from battery 90 through lead 128, armature 96, front contact and lead 9T to armature 103. At armature 103 the circuit divides, part of current passing Vvlirough lead 112, 'train line valve solenoid 113, and lead 117 bach to battery 90. The other branch of the divided circuit is traced frein armature 108 to back contact and lead 110, whistle valve solenoid 111, and leads 117 and to battery 90. The branch circuit last traced divides at bacl; contact 110 and part of the current finds .its Way through lead 11st, safety signal light tl, and lead 115 to battery 90. Thus safety is indicated by the green lainpsignal and the Whistle and train line valves are held closed;

As the movable unit nieves out of the block end zone one frequency only will be received by antenna 01, and therefore but one of the detectors vvill .be energized. Assuming that detector 0T (adjusted to a frequency of 22,000) is energized detector 75 is not energized, then relay 70 will continue to hold armatures 71 and 'Z2 attracted While relay does not attract 'ts armatures '79 and 80, armature 80 of course resting` against back contact 87. This completes a circuit frein battery 90 through lead 89, armature TQ, front contact and lead 8l, back contact and lead 87, armature 90, lead 92, armature 95, leads 93 and 91, to the relay 9st, Vwhich is preferably of the sloiv acting type to prevent breakingl of the circuit in the brief period between breal; and inalre of the armatures i2 and 80,. Otherwise a inalre before brealr armature would be necessary in place of those shown at 7T; and 80. From relay the circuit continues through lead 99, and lead 115 bach to lratteryV 90. Armature 9G bein held against front contact 97 completes the local circuits through its Attraction of the armaturesV Pill lli)

three parallel branches, thus maintaining the train line valve and Whistle valve closed and safety light Gr energized.

Assume that the movable unit has novvr passed into the next successive block.4 n so passing the alternate 'frequency of 27,000 Will be picked up by the antenna 61 and therefore detector (adjusted to a frequency olI 27,000) will respond and energize relay 78, which Will hold its armatures 7 9 and against their front contacts 83 andv and relay 70 will be (le-energized and it-s armatures 71 and 7 2 Will be released, ar mature 72 droppingl against its back contact-86. The local circuit will thus be closed throughrelay 94 as follows: from battery'90 to lead 88, armature 72, contact and lead 86, contact and lead 85, armature 80, Alead 192, armature 95, contactl and lead 93, leadv 91, relay 94, and leads 99 and 115 to battery 90. Armature 96 being retained against its iront Contact 97, completes the local circuit through its three parallel branches and thus maintaining the train line valve with Whistle valve closed and safety light G energized. IThe armature 96 is retained against its 'liront contact, Wherefore theV three parallel branches ot the :circuit compri-sing the lead 97, the safety light G, and the solenoids 111 and `113 will maintain thev train line valve and Whistle valvezin a closed condition, and the safety light G energized.

Assume that the radiation ot electromag netic Waves ifromboth Wave Wires 3 and 4 ceases for any reason. Detectors 67 and 75 will cease to energize relays 70 and 78 and their armatures 71, 72, 7 9 and 80 will drop away from the front contacts, 82, 8K1, 83 and 85 respectively. The armatures 72 and '80 will yengage their respective back contacts 86 and 87. It is readily understood that the circuits comprising the safety lamp G and the solenoids 111 `and 113 Will be opened by the above described displacement of the several armatures 71, 72, 78 and 80. The safety lamp G will then cease to glow and the solenoids 111 and 113 will no longer re tain their respective valves in a. closed condition, the valves opening to permit the whistle tofgive an audible signal and the brakes to frictionally engage the Wheels of the movable unit. A red light signalwill be given, by the closing of a circuit traceable as follows: from` battery 90, lead 128, armature 90, `back contact and lead 98, ,red lamp lt, 'and thence through leads 116-115 back to battery 90, a-s relay 911 has become deen'ergized owing to the dropping ott of the armatures 71, 72, 79 and 80.

The push button 107 can be used to energize train line valve solenoid 113 and thus hold the train line valve closed. The circuit closed bypressing button 107 is traced as follows: from battery' 90 through lead 128, armature 96, back contactand lead 98, lead cuit of train line valve solenoid 113, and

thuscloses the train line valve, the circuit beingtraced as follows: from battery through lead 117, solenoid Winding 113, lead 1 12, armature 103, front'contact and lead 109back contact and lead 98, armature 96.

and lead 128 `back to battery 90.

lissuming the radiations from Wavewire 3 to be absent due to any cause, and a responsive'device such as shownin Figure 5 to bein the zone ol'wvave Wire 4, the detector responsive to radiations ot' Wave Wire l Will, as it vpasses from its influence have its detector cease to energize its relay and thus both relays 70 and 787Would become deenergized, the green safety lamp will be extinguished, the red danger lamp Will be energized and the 'train` line and Whistle valves will be desenergized, as. and for the reasons heretofore explained. Y

It Will `be understood thatfwvhenever the car orlocomotive vcarrying` the equipment shown in Figure 5 Vis in a block, the Wave Wire assigned to Which is emanating Waves of the frequency to which .one oft the -detectorst and 75 is adjusted, the green lamp forming apart or' Athe carer locomotive equipment will be energized,'indicating that the block in advance o'f'that occupied by the ear or locomotive i-s unoccupied. Wvlien the propagation of Waves by said vave Wire ceases, the red danger lamp is energized and thcvvhistle `is caused to blow and the brakes are set to 'give the driver of the car or locomotive unmistakablenotice that the block in advance is occupied. VAsthe car or locomotive provided with the equipment of 'Figure 5 passes through a series ot unoccupied blocks, the safety indicati-on is maintained at all times, tirst by the energization of one of the detectors and then by the energization of the other. As the'car or locomotive passes irom one block into another, both detectors are simultaneously energized for a brief interval of time, with 'the result thatthe end of block indicator' `B gives the drivernotice that he is passing from one block into another. The purpose of the push button 107 is to enable the driver to proceedl With caution notwithstanding an in dication that the block ahead is not sate. He can, however, thus proceed under caution only With the danger lamp illuminated and the Whistle blowing.

tion of brakes in a blocl: adjoining an ofc-- cupied blocli, and a second application ot brakes at the entrance of the occupied bloeit. Antenna (S1 and detectors 0'1" l 75, relays and '78 are arranged and iunction the saine in Figure 1n 11' ire 0 the relavs r p "u 1:1 e i 0 and le have ar onai armatures 2&1

The remaining leads nl :ipp: L 1. the diagram, when indicaL bv ence characters as are curp K have functions siinilar lo the respcc niente oit 1V igure o.

1n our consideration oi" Figure 0 it will only be necessaryT for us to der fibe the tunetions and advantages of the additional. appah ratus *which distinguish the equipment olf Figure 0 from that shown in ill-ligure ii. liet us assuine that a locon'iotive provided with the responsive equipment ot Ylligure 0 .is in one of the blocks ot the railway shown iu Figure 2, and that the responsive apparatus has functioned to cause an application ot the brakes in a block in advance oli an occufiicd bloclr. Now 1ct us assrune tl it the driver has closed nianual switch 10i'A tor the purpose of holding the train line valve closed, and is proceeding under caution through the block in advance of the occupied bloeit, `with relays 2'0 and "i8 die-energized.

The ineans wliereby the switch 107A is adapted to hold the train line valver closed, comprises the armatures 81 and 231. idlhcnever both ot' the detectors 70 and 78 lail to receive radio 'frequent oscillations of proper frequencies, the armatures 81 and 231 Will rest against their respective back contacts 82 and 83. Closure of the switch 107A will permit a current to flow troni the battei 00 through lead 12S, armature 90, contact 00 lead 100, solenoid 101, lead 10o, switch 10i"A armature 81, contacts 02 and SES, armature 231 and through the The armature E201 connectedpermits current to tloiv troni the battery through lead 12S, armature 00, contact 9S, lead 100, relay 101, lead 105, arn'iature 102, Contact lead 1351A, armature 81, contacts 82 and 83, armature Q31 and thro the lead 88 bach to the battery 00. Solenoid 113 will be energized thus closing tbc train' line valve so that the train can proceed-under caution. The current energizing the solenoid 113 at this time will flow troni the battery 90 through the lead 128, contact contact 100, armature 103 solenoid 113 and through thellead 8S, bach to the battery 00. Closure of the switch 10TA will also close the circuit through G, viz, 00, 128, 00, 08, 100, 103, 114, Gf, 115, 90, and the appearance or" both R and .G will indicate to the e. that the apparatus is functioning correctly and that it is sate to proceed under caution.

lVith the train circuit so conditioned by the momentary closure o'l the switch 10i"A the train will approach the occupied block.

At the entrance oi the occupied block relay10 or 78 will be energized by the electroinagnetic Waves existent in that block. us assume that it is relay i 0 that becomes energized due to the Yfact that its associated detector 67 is detecting electro-magnetic Wares, propagated by the Wave Wire ot the occupied block. `The relay T0 will attract its armatures 71, T2, and 23 The armature 231 when disengaged 'troni the contact 88 ill open the holding circuit for the relay 1 01, the holding circuit as abore described comprising the battery 00, lead 128, armature 00, contact 08, lead 100, relay 101, lead armature 102, contact 100, lead 134:, arn'iature 81, contacts 02 and 3B, armature 231 and lead 88. The armatures 102, 130 and 103 ol the relay 101, will be released, thus opening the circuit comprising the battery 90, armature 06, contact 90 contact 109, armature 103, solenoid 113, and the lead 88. r1`he solenoid 113 will be cleanergized and the train line valve permitted lo open. 1t is apparent that the brakes oi'Y the movable unit will be applied then For the second time.

1n the foregoing description oi' the cir cuits illustrated in Figure 0, it was pointed out that as long as either ot the detectors 67 and 75 Were receiving eleitrosrnagnetic Waves of certain frequencies, the solenoids 111 and 113 would reinain energized. Powever, this Was subject to the assumption that at first, both of the detectors had been rcceiving electro-magnetic Waves sinuiltaueously, the Waves being of proper frequencies, and that the relay 91- had been energized. r1`he conditions resulting in a second application oit the brakes arise only atteitliere has been a total absence at any one time oi" radio frequent oscillations capable ot affecting the detectors. The absence of proper radio tre-- quent oscillations will result in de-ener iza- 

